Last year, Alex Rodriguez was Mr. Choke, because he was perceived as batting less well when the game was on the line. This year, he has hit a few walk-off homeruns, and he is the new Mr. Clutch.

Clutch hitting is one of those baseball notions that are constantly argued about. A short summary of the ongoing argument is: Inside baseball guys swear it is a true phenomena; statisticians generally cannot find it. I tend to believe that few if any players have consistently elevated their hitting in clutch situations, but you can find players whose hitting is worse, where the mental stress takes a toll. Tom Kirkendall points to this great blog I have never visited before called "Fire Joe Morgon." I am presuming the name is a reference to the fact that former player Joe Morgon has effectively staked himself out as the defender of baseball conventional wisdom against the assault of the Bill James / Billy Bean statistics guys. He has a great long post showing the absurdity of some of the clutch hitting claims. This one got him started:

It was a week ago today, fewer than 24
hours after the Pirates had put down a sizzling St. Louis rally in the
ninth inning, that catcher Ronny Paulino reflected upon it and offered
this surprising tidbit.

"You know what the key was to that whole inning?" he said. "When David Eckstein got hit by that pitch."

There's
a lot of stupid stuff in this article. I am happy to say -- since I get
bored of disparaging journalists only -- that most of it is said by
actual baseball players. That's new and fun!

David
Eckstein's career EqA is .260, which is exactly league average. Albert
Pujols's career EqA is .341, which is easy, don't-even-think-twice Hall
of Fame shoo-in. Anyone who ever wants to pitch to Albert Pujols over
David Eckstein in any situation, including pick-up whiffle ball games
at family barbecues when Pujols has dengue fever and Eckstein gets to
use one of those over-sized red bats while Pujols has to hit with a
live cobra, is a goddamn moron of the highest order.

Derek Jeter is generally considered the hands-down clutch playoff hitter in baseball today. Everyone in baseball, almost to a man, will say that Jeter steps up in the playoffs, so we see this:

Derek Jeter's Career Splits: .317/.388/.463

Derek Jeter's Career Postseason splits: .314/.384/.479

Mr.
Clutch is actually Mr. Exactly the Same No Matter What Month You Are
Talking About. He is Mr. Equally Excellent Hitting SS Every Month from
April to November. He is Mr. Outrageously Similar Statistics Every 30
Days.

The more important thing to watch out for would be the choke, which of course you could discern from the same statistics. But as a pitcher, you generally know where you fall in the line up and get a pretty good idea of who you'll be facing.

Someone with even a slight dip in their clutch statistics, a dip many would not think much about, would be indicative of a batter who definitely was not able to treat each at bat the same, regardless of circumstances.

Doesn't sound like much, but this is the guy you're going to try to finesse a little more at the plate. Depending on the pitcher's style, he might work harder at making him chase some junk, or throwing a couple hard and inside.